Implanting brachytherapy seeds into a patient typically involves loading a number of such seeds, possibly including spacers between successive and either loosely or within a carrier strand, into a brachytherapy implantation needle. The needles are typically formed from a medically-compliant metal, such as stainless steel. The loaded needle typically includes the seeds at one end within the needle and a stylet extending from the seeds out the opposite end of the needle. A grid, or template, providing guide-holes is sometimes positioned against the patient so that the physician may accurately guide the seeds to their proper location in or about the target tissue by inserting the needle through the proper hole in the grid. The grid body, being about one-inch thick, receives and provides some support to the sharpened end of the needle. The physician typically drives the needle into the patient by grasping the needle by its hub at the free end. It is preferable to hold the needle by the hub so as to reduce the exposure of the hands to the radioactivity of the seeds at the far end. However, as the grid body holds the sharp end of the needle and the physician holds the needle by the hub at the opposite end, dermal resistance to being punctured can lead to buckling stresses on the needle, causing the needle to deflect or bow quite noticeably. Once the needle begins to penetrate the through the dermis into the perineum, the buckling problem dissipates as the inner tissue provides much less resistance than the dermis.
The buckling problem has been more pronounced as the delivery needles get smaller in size. For example, the brachytherapy seeds sold as THINSEED™ (marketed by the General Electric Company through its GE Healthcare business) may be implanted using a 20 gage needle. The buckling problem has been observed in some early procedures using THINSEED. As the needle passageway is typically filled throughout its length by seeds and/or spacers and the stylet, permanent deformation of the needle due to the penetration compression forces applied to it is less likely. Nevertheless, physicians report that the bowing of the needle can be a distraction in performing the operation. Physicians will typically hold the needle body with one hand as the other pushes on the needle hub to drive the needle into the patient. Such a manual technique increases physician exposure to the activity of the loaded needles. While thicker needles could be employed, thinner needles are desirable for the lower insult caused to the patient by the smaller tissue displacement as the needle passes and the thinner seeds remain implanted.
There is therefore a need for a device that will limit the deflection of a brachytherapy needle during penetration. The device should desirably allows the physician to maintain some stand-off from the seeds within the needle so as to help minimize extremity exposure to the activity of the brachytherapy seeds.